The present invention relates amplification-type CMOS solid-state image pickup apparatus which amplify electric charges obtained by photoelectric conversion elements provided in a plurality of arrayed pixels and output amplified electric charges as electric signals.
In recent years, there have been widely used image pickup apparatus, such as digital still cameras and digital video cameras, which can pick up an image by means of a solid-state image sensing device and store the picked-up image as digital data. Formerly, CCD (Charged Coupled Device) solid-state image pickup apparatus were the most common type of solid-state image pickup apparatus. In recent years, however, CMOS (Complementary Metal Oxide Semiconductor) solid-state image pickup apparatus have been attracting a lot of attention (see for example Japanese Patent No. 3,827,145) because the demand for an increased number of pixels is getting stronger and stronger. Many of the CMOS solid-state image pickup apparatus have an electronic shutter function. Unlike the shutter function of the CCD solid-state image pickup apparatus, the electronic shutter function of the CMOS solid-state image pickup apparatus is implemented by a so-called “rolling shutter” or “focal plane shutter”, which outputs signals by sequentially scanning a multiplicity of two-dimensionally arrayed pixels on a row-by-row basis. Thus, with the conventionally-known CMOS solid-state image pickup apparatus, the exposure period (timing) sequentially shifts row by row, so that, in imaging a moving object, the image of the moving object would be undesirably distorted. To avoid this problem, various techniques have been proposed which allow the CMOS solid-state image pickup apparatus to have a “global shutter function” for exposing all of the pixel rows during the common or same exposure period. For example, in a CMOS solid-state image pickup apparatus disclosed in Japanese Patent Application Laid-open Publication No. 2006-191236, exposure of photoelectric conversion elements in the form of photodiodes is started with a transfer transistor and reset transistor, provided per pixel, placed in an ON state and with a stored (or accumulated) electric charge and potential of a floating diffusion layer of each of the photodiodes placed in a reset state. After the passage of a predetermined exposure period, the disclosed CMOS solid-state image pickup apparatus closes a mechanical shutter to terminate the exposure period and then sequentially reads out, from the floating diffusion layers, voltages corresponding to electric charges transferred from the photodiodes on the row-by-row basis.
However, if the mechanical shutter is provided for the global shutter function as disclosed in the No. 2006-191236 publication, the CMOS solid-state image pickup apparatus would be undesirably complicated in mechanical construction and hence become expensive.